1. Field of the Invention
This invention concerns air gaging and more specifically air gaging fixtures of the type adapted to measure eccentricity between bores and countersunk portions of such bores, such as valve stem holes and valve seats.
2. Description of the Prior Art
In the machining of valve seats and stem holes in cylinder heads for internal combustion engines, various machining errors can produce eccentricity between the stem hole and the valve seat and out-of-square conditions between the centerline of the stem hole and the valve seat and out-of-round conditions of the valve seat, all of which can cause poor seating of the valve in the valve seat creating leakage and poor engine performance, as well as increased emissions levels These conditions have in the past been detected by means of an arrangement including a solid arbor element located in the valve stem hole and an air spindle slip fit over the solid arbor having air jets arranged to contact the valve seat. If the stem was eccentric with respect to the valve seat, the air spindle would not seat on the valve seat surface and air flow through the jets would indicate an eccentric conditon. The problem with this approach is that a number of error conditons can effect seating of the air spindle and the resulting signals interpreted mistakenly as resulting from eccentricity. That is, if the stem hole is out-of-square with respect to the valve seat or the valve seat itself is out-of-round or there are irregular surface conditions on the valve seat, the air spindle would ride up on the arbor. It should be noted that in order to correct each of these conditions, it would be advantageous to know specifically which of these conditions existed. The object of this invention is to provide such an indication of such eccentricity only, unifluenced by out-of-round, out-of-square or irregular surface conditions, and also is adapted to independently indicate variations in surface conditions.